JP4224871B2 - Manufacturing method of semiconductor substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor substrate used as a material for a semiconductor device.
[0002]
[Prior art]
A semiconductor substrate used as a material for a semiconductor device is manufactured by growing a silicon single crystal ingot by the CZ method or the FZ method, and cutting a wafer from the ingot. This manufacturing method is described, for example, in Precision Machine 51/7/1985 “Silicon Crystal and Wafer Processing”. The details of the process of obtaining the product wafer from the ingot are as follows.
[0003]
The silicon single crystal ingot grown by the CZ method or the FZ method is cut into a plurality of blocks 1, 1... As shown in FIG. As shown in FIG. 7B, each block 1 is rounded into blocks 2 having a constant diameter by external grinding. In some cases, each block may be cut after rounding. As an external grinding machine used for rounding, a diamond cup wheel grinder is generally used and is commercially available as a cylindrical three-dimensional grinding machine.
[0004]
When the rounding process is finished, the crystal orientation of the block 2 is confirmed by X-rays, and an orientation flat (hereinafter referred to as orientation flat) or notch showing the crystal orientation is machined over the entire length of a part of the outer peripheral surface in the circumferential direction. The block 2 subjected to this processing is sliced into a plurality of wafers 3, 3... By an inner peripheral blade or a wire saw as shown in FIG.
[0005]
For each wafer 3, first, as shown in FIG. 7 (d), chamfering is performed for the purpose of preventing chipping of the peripheral portion and chip. Next, in order to make the thickness of the wafer 3 uniform, lapping is performed. Lapping is a process in which a polishing liquid is injected between a surface plate and a workpiece, and the surface of the workpiece is polished by the movement or scratching action of the polishing liquid by the rotation of the surface plate.
[0006]
When the lapping is completed, as shown in FIG. 7E, the entire surface of the wafer 3 is dissolved by etching. The purpose of the etching is to remove the processing strain layer 4 formed by conventional machining, to reduce the surface roughness, to flatten the surface. As an etchant, an acid solution obtained by adding acetic acid as a moderator to a mixed solution of hydrofluoric acid and nitric acid is often used, but an alkaline solution obtained by adding a surfactant to KOH, NaOH, or the like is also used in part. .
[0007]
When the etching is finished, although not shown in the drawing, processing distortion is applied to the back surface by sandblasting for gettering, and a Donakiller treatment is performed at 650 ° C. At present, since the processing strain on the back surface becomes a dust generation source in the device process, a polysilicon film may be formed on the back surface. In some cases, oxygen precipitation nuclei are grown at a temperature of about 650 ° C. for the purpose of IG. Furthermore, an oxide film may be formed on the back surface by CVD for the purpose of preventing autodoping during epi growth described later.
[0008]
Finally, by polishing the surface, a silicon wafer having a mirror surface can be obtained. This surface polishing has been conventionally performed only on one side, but the number of cases where it is performed on both sides is increasing due to the demand for high accuracy. In order to achieve high accuracy, high-precision and low-damage surface grinding may be performed before surface polishing. In order to reduce dust generation and chipping in the device process, the chamfered surface may be polished to a mirror surface before the surface polishing.
[0009]
Further, in addition to the above steps, there are cases where heat treatment at a high temperature or epilayer growth is performed for the purpose of improving the crystal quality of the surface layer, which is a device forming layer of a silicon wafer. Cleaning is performed as appropriate.
[0010]
[Problems to be solved by the invention]
In such a conventional method for manufacturing a semiconductor substrate, many steps are required to obtain a product wafer from an ingot. With only the main ones, collection of block 1 by ingot cutting, rounding to constant diameter block 2 by external grinding, processing of orientation flat or notch indicating crystal orientation, sampling of wafer 3 by slicing, chamfering of wafer peripheral part There are lapping for making the wafer thickness uniform, etching for removing the processing strain layer, mirror processing by surface polishing, and the like.
[0011]
Among these processes, for example, chamfering of the peripheral edge of the wafer is performed on each of a large number of wafers 3, 3... Cut out from the block 2. Requires a processing machine. Etching for removing the processing strain layer is also performed on each of the plurality of wafers 3, 3.
[0012]
Due to these circumstances, the amount of capital investment required to obtain product wafers from ingots is still enormous, and it is possible to manufacture substrates with larger diameters from the current level and to achieve higher flatness due to higher device integration. In addition, in order to meet the demand for mirror-finishing of the back surface and outer peripheral surface, the amount is expected to increase further, and an increase in manufacturing cost due to this is a major problem.
[0013]
An object of the present invention is to provide a semiconductor substrate manufacturing method capable of manufacturing a high-quality semiconductor substrate at a lower cost than conventional ones.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention as set forth in claim 1 is characterized in that, before cutting a single crystal wafer from a single crystal ingot, a plurality of annular convex portions that are continuous in the circumferential direction are provided on the outer peripheral surface of the single crystal ingot. An outer surface machining step formed at predetermined intervals in the direction, an outer surface finishing step for removing a processing strain layer generated on the outer surface of the single crystal ingot by the outer surface machining step , and a single crystal ingot after the outer surface finishing step. A film forming step of forming a protective film on the outer peripheral surface of the substrate, and after this film forming step, the single crystal ingot is cut between two adjacent annular projections to cut out a plurality of single crystal wafers from the single crystal ingot. And a slicing step .
[0015]
According to the second aspect of the present invention, before cutting the single crystal wafer from the single crystal ingot, a plurality of annular convex portions that are continuous in the circumferential direction are formed on the outer peripheral surface of the single crystal ingot at predetermined intervals in the axial direction. An outer surface processing step and an outer surface finishing step of removing the processing strain layer generated on the outer peripheral surface portion of the single crystal ingot by the outer surface processing step, and processing the outer peripheral surface of the single crystal ingot into a mirror surface after removing the processing strain layer Then, after this outer surface finishing step, a film forming step of forming a protective film on the outer peripheral surface of the single crystal ingot, and after this film forming step, the single crystal ingot is cut between two adjacent annular projections. And a slicing step of cutting a plurality of single crystal wafers from the single crystal ingot.
[0016]
According to a third aspect of the present invention, there is provided a method for manufacturing a semiconductor substrate according to the first or second aspect, further comprising a wafer finishing step of finishing a single crystal wafer into a product after the slicing step. is there.
[0017]
The present invention is defined in claim 4, in the wafer polishing step, a method of manufacturing a semiconductor substrate according to claim 3, characterized in that processing the surface of the wafer, leaving a protective film on the outer peripheral surface of the wafer It is.
[0018]
In the method for manufacturing a semiconductor substrate according to the present invention, before the outer surface processing, the processing that represents the crystal orientation in a part of the outer peripheral surface of the ingot in the circumferential direction can be performed over the entire length in the axial direction. In that case, the annular convex portion formed on the outer peripheral surface of the ingot is not continuous to the entire circumference. The annular convex portion that is continuous in the circumferential direction does not mean a portion that is continuously continuous over the entire circumference, but includes a portion that is divided at a portion in the circumferential direction.
[0019]
The annular convex portion can have a shape corresponding to the peripheral shape of the single crystal wafer that has undergone chamfering.
[0020]
The outer surface processing may be chemical such as etching, but from the viewpoint of efficiency, machining for grinding the outer peripheral surface of the ingot is preferable.
[0021]
In the outer surface processing, rounding processing, uneven processing and chamfering processing can be performed simultaneously. Thereby, simplification of a process is achieved.
[0022]
After the outer surface processing, it is possible to perform an outer surface finish for removing the processing strain layer generated on the outer peripheral surface layer portion of the single crystal ingot by the processing. For example, etching can be used as the outer surface finish. In this outer surface finishing, the outer peripheral surface of the single crystal ingot can be processed into a mirror surface after removing the processing strain layer.
[0023]
After the outer surface processing, film forming for forming a protective film on the outer peripheral surface of the single crystal ingot is performed. When the outer surface finish is performed, filming is performed after the outer surface finish. This filming protects the peripheral edge of the wafer in later slices. Examples of the protective film include a thermal oxide film and a resin coating film in addition to an oxide film formed by CVD.
[0024]
After the slicing, a wafer finishing process for finishing the single crystal wafer into a product can be performed. Examples of the wafer finishing process include lapping or surface grinding. As a result, the wafer surface is flattened and the wafer thickness is made uniform. Polishing can be performed after lapping or surface grinding. By this polishing, the processing strain layer on the wafer surface is removed. Moreover, the surface is finished to a mirror surface. After the polishing, in order to improve the flatness, plasma etching as described in the monthly Semiconductor World 19944.4 "SOI wafer processing technology" can be performed. In these wafer finishing processes, the peripheral portion is protected by leaving a protective film on the outer peripheral surface of the wafer.
[0025]
In the method of manufacturing a semiconductor substrate according to the present invention, a single crystal having a special shape such that a plurality of chamfered single crystal wafers are overlapped and integrated in an outer surface processing step before cutting a single crystal wafer from a single crystal ingot. Ingots are manufactured.
[0026]
If such a single crystal ingot having a special shape is manufactured, first, the chamfering of the wafer peripheral portion is efficiently carried out collectively in the state of the ingot, and the chamfering in the state of the wafer which is troublesome is unnecessary. Become. Secondly, the etching for removing the processing strain layer is also efficiently carried out collectively in the ingot state, and the etching in the wafer state which is troublesome becomes unnecessary. Third, the rounding process for making the diameter of the ingot constant is also unnecessary. Fourth, when the outer peripheral surface of the wafer is mirror-finished, the processing is efficiently performed in an ingot state. Fifth, even when the peripheral edge of the wafer is protected with a protective film, the filming is efficiently carried out collectively in an ingot state.
[0027]
Filming not only protects the peripheral edge of the wafer by slicing, but also effectively protects the peripheral edge of the wafer by subsequent lapping or surface grinding.
[0028]
As a result, a high-quality semiconductor substrate is manufactured at a low cost.
[0029]
Further, as an external surface processing apparatus used in the method for manufacturing a semiconductor substrate of the present invention, a means for supporting a single crystal ingot to rotate in the circumferential direction and a rotation center line of the single crystal ingot rotating in the circumferential direction are parallel. An outer surface grinding apparatus provided with a grinding roll that is provided and forms an annular convex portion continuous in the circumferential direction on the outer peripheral surface of the single crystal ingot by pressing the grooved outer peripheral surface against the outer peripheral surface of the single crystal ingot. It is done. With this apparatus, the rounding process, the concavo-convex process and the chamfering process can be simultaneously performed by efficient machining, and the above-described single crystal ingot having a special shape can be economically manufactured.
[0030]
The grinding roll preferably has a configuration in which a plurality of grooves are continuously provided in the axial direction on the outer peripheral surface in order to simultaneously form a plurality of annular convex portions.
[0031]
Further, as another external surface processing apparatus used in the method for manufacturing a semiconductor substrate of the present invention, means for rotating in the circumferential direction by supporting a single crystal ingot in which an annular convex portion continuous in the circumferential direction is formed on the outer peripheral surface is provided. And a roll-shaped polishing pad that is provided parallel to the rotation center line of the single crystal ingot rotating in the circumferential direction and that presses against the outer peripheral surface of the single crystal ingot to polish the surface of the annular convex portion. An external surface polishing apparatus is mentioned. With this apparatus, mirror processing of the annular convex portion can be efficiently performed by mechanochemical processing.
[0032]
Moreover, the single crystal ingot obtained by the method for manufacturing a semiconductor substrate of the present invention is a specially shaped ingot having a plurality of annular projections arranged on the outer peripheral surface in parallel in the axial direction and arranged in parallel at predetermined intervals. Yes, a wafer that does not require chamfering or etching can be provided by cutting the wafer from the ingot.
[0033]
The annular convex part here can also be made into the shape corresponding to the peripheral part shape of the single crystal wafer which received the chamfering process.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0035]
1 is a process diagram of a semiconductor substrate manufacturing method according to an embodiment of the present invention, FIG. 2 is a front view of an external surface processing apparatus (external surface grinding apparatus) used in the manufacturing method, and FIG. 3 is capable of processing a notch portion. FIG. 4 is a side view showing the processing of the notch portion by the external surface processing apparatus, and FIG. 5 is another external surface processing apparatus (external surface polishing apparatus) used in the manufacturing method. FIG. 6 is a front view of another grinding roll.
[0036]
In the method of manufacturing a semiconductor substrate according to the embodiment of the present invention, first, as shown in FIG. 1A, a silicon single crystal ingot 10 grown by a CZ method or an FZ method includes a plurality of blocks 11, 11,. Is cut and separated.
[0037]
For each block 11, first, the crystal orientation is confirmed by X-rays, and an orientation flat or notch indicating the crystal orientation is processed in the circumferential direction part of the outer circumferential surface over the entire axial length. When the orientation flat or notch is formed, as shown in FIG. 1B, the outer peripheral surface of the block 11 is ground so as to correspond to the predetermined crystal orientation of the single crystal wafer obtained by slicing. A plurality of annular convex portions 12, 12,... Continuous in the circumferential direction are formed on the outer peripheral surface at predetermined intervals in the axial direction.
[0038]
Each annular convex portion 12 has a substantially semicircular cross-sectional shape corresponding to the peripheral portion shape of the single crystal wafer that has undergone chamfering. The width W of the annular protrusion 12 corresponds to the thickness of the wafer sliced from the block 11, that is, the final thickness T of the wafer + the double-sided machining allowance (t1 + t2) of the wafer, and is formed between the adjacent annular protrusions 12 and 12. The width w of the annular groove 13 corresponds to the slice allowance S [see FIG. 1 (e)].
[0039]
For this outer surface processing, for example, an outer surface processing device 20 shown in FIG. 2 is used. The outer surface processing apparatus 20 shown in FIG. 2 includes means for supporting the block 11 and rotating it in the circumferential direction, and a grinding roll 21 pressed against the outer peripheral surface of the block 11. The grinding roll 21 has a configuration in which a predetermined number of grinding disks 22, 22... Are connected in the axial direction and integrated, and the central axis thereof is parallel to the rotation center line of the block 11. Each grinding disk 22 is a grooved disk having an annular groove having a cross-sectional shape corresponding to the annular protrusion 12 on the outer peripheral surface, and the outer peripheral surface is an uneven grinding surface on which diamond is deposited. A plurality of the uneven grinding surfaces may be formed in the axial direction.
[0040]
By rotating the block 11 in the circumferential direction and applying the grinding liquid to the outer peripheral surface of the block 11 and pressing the grinding roll 21 against the outer peripheral surface, a predetermined number of annular convex portions 12, 12,. It is formed. When the formation of the predetermined number of annular protrusions 12, 12,... Is finished, the grinding roll 21 is once separated from the block 11, the block 11 is moved in the axial direction, and the predetermined number of annular protrusions 12, 12,. Form. By repeating this, annular convex portions 12, 12,... Are formed on the entire outer peripheral surface of the block 11, and a block 14 having a special shape such as a plurality of chamfered single crystal wafers stacked and integrated is obtained. Manufactured.
[0041]
That is, according to the outer surface processing apparatus 20 shown in FIG. 2, the rounding process for constant diameter, the uneven | corrugated process, and the chamfering process are performed simultaneously.
[0042]
There is no problem when an orientation flat is formed on the outer peripheral surface of the block 11, but when a notch is formed, the grinding disk 22 does not enter the notch portion in the outer surface processing apparatus 20 of FIG. Processing cannot be performed. Therefore, for example, the notch portion is chamfered using an outer surface processing apparatus 30 shown in FIG.
[0043]
The outer surface processing apparatus 30 shown in FIG. 3 includes means for supporting the specially shaped block 14 and rotating it in the circumferential direction, and a grinding roll 31 pressed against the outer peripheral surface of the block 14. The grinding roll 31 has an integral structure in which small-diameter grinding disks 32, 32,. When the grinding roll 31 is pressed against the outer peripheral surface of the block 14 while rotating, and the block 14 is rotated at a low speed, each grinding disk 32 of the grinding roll 31 passes through the notch portion 15 of the block 14, as shown in FIG. The notch 15 is chamfered.
[0044]
Here, the formation of the notch portion, the formation of the annular projections 12, 12,... By the outer surface processing device 20, and the chamfering of the notch portion by the outer surface processing device 30 were performed in order, but the outer surface processing device 30 was used from the beginning. The formation of the notch portion, the formation of the annular convex portions 12, 12,... And the chamfering of the notch portion can be performed simultaneously. Further, when forming the orientation flat, the orientation flat and the annular convex portions 12, 12,... Can be simultaneously formed using the outer surface processing device 30.
[0045]
The cross-sectional shape of the annular convex portion 12 is a semicircular shape here, but may be a trapezoidal shape. In that case, grinding rolls 21 and 31 as shown in FIG. Moreover, although the bottom face shape of the annular groove 13 formed between the adjacent annular convex parts 12 and 12 is flat in the axial direction, it may be semicircular. In that case, grinding rolls 21 and 31 as shown in FIG.
[0046]
When the block 14 having a special shape is manufactured, as shown in FIG. 1C, etching is performed to remove the processing strain layer 16 existing on the outer peripheral surface portion of the block 14. As the etching solution, a mixed solution of hydrofluoric acid and nitric acid, or an alkaline solution obtained by adding a surfactant to KOH, NaOH, or the like is used. It is possible to hold the block 14 at both end surfaces and rotate the block 14 or to stir the etching solution so that the outer peripheral surface of the block 14 is uniformly etched.
[0047]
When the etching is finished, the outer peripheral surface of the block 14 is mirror-polished by, for example, an outer surface processing apparatus 40 shown in FIG. The outer surface processing apparatus 40 includes means for supporting and rotating the specially shaped block 14 and roll-shaped polishing pads 41 and 42 pressed against the outer peripheral surface of the block 14. Although the polishing pad 41 is a straight body roll, the outer peripheral surface of the polishing pad 42 is provided with annular grooves 43, 43... Having a cross-sectional shape corresponding to the annular protrusion 12. The polishing slurry is supplied to the outer peripheral surface of the block 14 and pressed against the outer peripheral surface while rotating the polishing pads 41, 42, so that the tip surfaces of the annular protrusions 12, 12. 42, each side surface of the annular projections 12, 12,... Is mirror-polished.
[0048]
If the processing strained layer 16 can be removed by mirror polishing, it is possible to omit the etching and perform mirror polishing directly.
[0049]
When the mirror polishing of the outer peripheral surface of the block 14 is finished, a protective film 17 is formed on the outer peripheral surface as shown in FIG. As a method for forming the protective film 17, for example, there is a method in which a resin is applied to the outer peripheral surface of the block 14, or an OCD (SiO ₂ coating forming coating solution) is applied and cured by heating.
[0050]
As another forming method, there is a method of forming an oxide film or a nitride film at about 700 ° C. using a low pressure CVD furnace. In this case, since the growth of oxygen precipitation nuclei can be promoted by the heat treatment for film formation, the IG source can be formed. Further, irregularities are formed on the outer peripheral surface of the block 14, the surface area thereof is large, and the cooling rate is increased, so that donor killer treatment is also possible.
[0051]
As another forming method, there is a method of forming a thermal oxide film by performing a heat treatment at, for example, about 800 to 1000 ° C. in an oxidizing atmosphere using a diffusion furnace. In this case as well, IG source formation and donor killer treatment are possible.
[0052]
Also during film formation, the block 14 is held at both end faces in the same way as during etching to protect the outer peripheral surface.
[0053]
When the film formation is finished, as shown in FIG. 1 (e), the block 14 is set in a slicing machine so that the crystal plane becomes a predetermined plane, and the block 14 is placed between the adjacent annular convex portions 12 and 12. A plurality of wafers 18, 18,... Are cut out from the block 14 by cutting. The slicing machine may be a wire saw or an inner peripheral saw. In this processing, since the outer peripheral surface of the block 14 is protected by the protective film 17, damage and dirt on the outer peripheral surface are prevented. The cut out wafer 18 has already been chamfered and mirror finished on the outer peripheral surface, and the finished surface is still protected by the protective film 17.
[0054]
For each wafer 18, first, lapping or surface grinding is performed on both surfaces with the protective film 17 left on the outer peripheral surface in order to flatten the sliced surface and make the wafer thickness uniform. The surface grinding on both sides may be performed on each side or simultaneously on both sides. Moreover, you may perform the single side | surface or double-sided surface grinding after lapping. In this processing, since the protective film 17 is left on the outer peripheral surface of the wafer 18, damage and dirt on the outer peripheral surface are prevented.
[0055]
When the flattening of the slice surface and the uniformization of the wafer thickness are finished, as shown in FIG. 1 (f), the outer peripheral surface of the wafer 18 is protected in order to remove the processed strain layer 19 on the surface and make the surface mirror. Both surfaces are polished with the film 17 left. The polishing on both sides may be performed on each side or on both sides simultaneously. Even in this processing, since the protective film 17 is left on the outer peripheral surface of the wafer 18, damage and contamination of the outer peripheral surface are prevented.
[0056]
When there is no possibility of damage or contamination of the outer peripheral surface or when the protective film 17 may adversely affect the polished surface, polishing may be performed after removing the protective film 17. In other cases, as shown in FIG. 1G, after the polishing, the protective film 17 is removed and cleaning is performed. The protective film 17 is removed using HF if the protective film 17 is an oxide film, and using a solvent if it is an epoxy resin.
[0057]
Through the above process, a high-quality wafer 18 whose both surfaces are mirror-polished and whose outer peripheral surface is chamfered and mirror-polished has been manufactured in a smaller number of processes than before, and without causing chipping or contamination of the peripheral edge. The
[0058]
In the above embodiment, by forming the annular protrusions 12, 12... On the outer peripheral surface of the ingot 11, the rounding process for the constant diameter, the concavo-convex process, and the chamfering process are performed simultaneously, but the rounding for the constant diameter is performed. It is also possible to perform uneven processing and chamfering after processing. Further, the concavo-convex processing and chamfering may be performed by performing chamfering after the concavo-convex processing.
[0059]
In wafer processing, CVD oxide film formation on the back surface, formation of a polysilicon film as EG, high-temperature heat treatment for forming a defect-free layer on the surface layer, plasma etching processing for improving flatness between appropriate processes Etc. can be added as appropriate. In this case, when the protective film is a resin film, it is preferable to remove the protective film before the heat treatment. It is also possible to perform epi growth after polishing.
[0060]
The cleaning is appropriately performed at a necessary stage.
[0061]
【The invention's effect】
As described above, the method for manufacturing a semiconductor substrate of the present invention performs chamfering on a large number of wafers very simply by performing a process of forming a plurality of annular protrusions on the outer peripheral surface in an ingot state. be able to. Moreover, the rounding process for the constant diameter of an ingot can be abbreviate | omitted. Furthermore, etching on a large number of wafers can be omitted. By these, it becomes possible to manufacture a high-quality wafer efficiently and at low cost.
[Brief description of the drawings]
FIG. 1 is a process diagram of a semiconductor substrate manufacturing method according to an embodiment of the present invention.
FIG. 2 is a front view of an outer surface processing apparatus (outer surface grinding apparatus) used in the manufacturing method.
FIG. 3 is a front view of an outer surface processing apparatus (outer surface grinding apparatus) capable of processing a notch portion.
FIG. 4 is a side view showing processing of the notch portion by the outer surface processing apparatus.
FIG. 5 is a front view of an outer surface processing apparatus (outer surface polishing apparatus) used in the manufacturing method.
FIG. 6 is a front view of another grinding roll.
FIG. 7 is a process diagram of a conventional method for manufacturing a semiconductor substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Single-crystal ingot 11 Block cut out from single-crystal ingot 12 Annular convex part 13 The annular groove formed between adjacent annular convex parts 14 The special-shaped block in which the annular convex part was formed 15 Notch part 16 Processing of outer peripheral surface Strain layer 17 Protective film 18 Single crystal wafer 19 Wafer surface processing strain layer 20, 30 External surface processing device (external grinding device)
21 31 Grinding roll 22 32 Grinding disk 40 External surface processing device (external surface polishing device)
41, 42 Polishing pad

Claims (4)

Before cutting a single crystal wafer from a single crystal ingot, an outer surface machining step for forming a plurality of annular convex portions continuous in the circumferential direction at predetermined intervals on the outer circumferential surface of the single crystal ingot, and this outer surface machining step An outer surface finishing step for removing the processing strain layer generated on the outer peripheral surface layer portion of the single crystal ingot, a film forming step for forming a protective film on the outer peripheral surface of the single crystal ingot after the outer surface finishing step , and this film attaching step And a slicing step of cutting a single crystal ingot between two adjacent annular convex portions to cut out a plurality of single crystal wafers from the single crystal ingot. Before cutting a single crystal wafer from a single crystal ingot, an outer surface machining step for forming a plurality of annular convex portions continuous in the circumferential direction at predetermined intervals on the outer circumferential surface of the single crystal ingot, and this outer surface machining step An outer surface finishing step of removing the processed strain layer generated on the outer peripheral surface layer of the single crystal ingot, processing the outer peripheral surface of the single crystal ingot into a mirror surface after removing the processed strain layer, and after the outer surface finishing step, A film forming step of forming a protective film on the outer peripheral surface of the crystal ingot, and after this film forming step, the single crystal ingot is cut between two adjacent annular projections to form a plurality of single crystal wafers from the single crystal ingot. And a slicing step of cutting out the semiconductor substrate. 3. The method of manufacturing a semiconductor substrate according to claim 1, further comprising a wafer finishing step of finishing a single crystal wafer into a product after the slicing step . 4. 4. The method of manufacturing a semiconductor substrate according to claim 3 , wherein, in the wafer finishing step, the surface of the wafer is processed with a protective film left on the outer peripheral surface of the wafer .

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